Yes they do, USB-C cables with Thunderbolt is different from regular USB-C on account of the 2 data pins added.
So none of the USB-C cables I bought would enable me to use external monitors with my hardware because it supported 2 displays over TB only. But the connectors aren’t even keyed so it’s just an irritating mess to keep track of what is and isn’t.
However it would be a great system if TB over USB-C was the default and only probably.
You are mistaken. Thunderbolt alternate mode does not require any additional pins, it does require special cabling though. Most Thunderbolt cables are not capable of any 5-10(-20) gbps USB but they are still using the exact same connector.
USB 4 will change this in that Thunderbolt cables will now be compatible with everything.
The only thing you possibly could think of is VirtualLink which repurposed the existing USB 2.0 pins for two more high speed lanes but even that is using the exact same physical connector.
So none of the USB-C cables I bought would enable me to use external monitors with my hardware because it supported 2 displays over TB only. But the connectors aren’t even keyed so it’s just an irritating mess to keep track of what is and isn’t.
However it would be a great system if TB over USB-C was the default and only probably.